Tune evacuation candidate selection.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 684 matching lines @@
     CHECK(p->slots_buffer() == NULL);
     DCHECK(p->area_size() == area_size);
     int live_bytes =
         p->WasSwept() ? p->LiveBytesFromFreeList() : p->LiveBytes();
     pages.push_back(std::make_pair(live_bytes, p));
   }
 
   int candidate_count = 0;
   int total_live_bytes = 0;
 
-  bool reduce_memory =
-      heap()->ShouldReduceMemory() || heap()->HasLowAllocationRate();
+  // The minimum about of memory to make aggresive compaction worthwhile.

[Hannes Payer (out of office), 2015/10/01 14:36:07]

amount

+  const int kMinPagesToReduceMemory = 16;
+
+  bool reduce_memory = heap()->ShouldReduceMemory() ||
+                       (heap()->HasLowAllocationRate() &&

[Hannes Payer (out of office), 2015/10/01 14:36:07]

As you suggested offline, we can remove the allocation rate heuristic here.

+                        number_of_pages > kMinPageToReduceMemory);
   if (FLAG_manual_evacuation_candidates_selection) {
     for (size_t i = 0; i < pages.size(); i++) {
       Page* p = pages[i].second;
       if (p->IsFlagSet(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING)) {
         candidate_count++;
         total_live_bytes += pages[i].first;
         p->ClearFlag(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING);
         AddEvacuationCandidate(p);
       }
     }
@@ skipping 3882 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(&rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8